Hydraulically powered pump having a precompression function

ABSTRACT

An hydraulically powered multiplex pump having at least three pumping units, each operable in a cycle including suction, precompression and discharge phases, with the cycles being out of phase with one another, whereby simultaneous performance of these functions results in a substantially constant pressure and flow of both the pumped fluid and the power fluid. Separate power and cycle control circuits, which may employ different fluids, are provided. Control valve assemblies, each including two sleeve valves communicating with a common chamber, are operated by the control circuit fluid to condition power circuit flow for the various phases of the pumping cycle. The power end of the pumping units includes power cylinders which may be fluid interconnected at their rod ends so that operations in each power cylinder affect functions in the other chambers, and provision is made for automatic correction of errors in stroke length.

' Oct. 16, 1973 ABSTRACT Primary Examiner-Alan Cohan Attorney-Burns, Doane, Swecker & Mathis An hydraulically powered multiplex pump having at least three pumping units, each operable in a cycle including suction, precompression and discharge phases, with the cycles being out of phase with one another, whereby simultaneous performance of these functions results in a substantially constant pressure and flow of both the pumped fluid and the power fluid. Separate power and cycle control circuits, which may employ 137/624' different fluids, are provided. Control valve assem- Flsb 13/02 blies, each including two sleeve valves communicating 137/624'1 with a common chamber, are operated by the control circuit fluid to condition power circuit flow for the various phases of the pumping cyclev The power end of the pumping units includes power cylinders which may be fluid interconnected at their rod ends so that operations in each power cylinder affect functions in the other chambers, and provision is made for automatic correction of errors in stroke length.

10 Claims, 18 Drawing Figures Faldi Seigden......

United States Patent Cole HYDRAULICALLY POWERED PUMP HAVING A PRECOMPRESSIQN FUNCTION [76] Inventor: Clinton W. Cole, PO. Box 1431,

Duncan, Okla. 73533 Dec. 3, 1971 [22] Filed:

[21] Appl. No.: 204,586

Related U.S. Application Data [62] Division of Ser. No. 886,687, Dec. 19, 1969, Pat. No.

[52] U.S. Cl... 137/596.12, l37/596.18, l37/596.14,

[51] Int.

[58] Field of Search..................

References Cited UNITED STATES PATENTS a P 9 5 9 l. l 2 1 PATENTEnnm 16 1975 SNEU 02 N16 FIG.3

FMFNTEDUBI 16 L973 SHEET 03 0F 16 FIG.4

PAIENTED UN 16 I975 SHEET 0; 0F 16 SHKU 07 W16 PATENTEU UN 16 1973 m l .m

WHHEDnm 16 ms 3.765.449

sum 0a or 16 FIG.9A2

i VALVE cowomow VALVE OPERATION VALVES i A PRESSURIZED 21 OPENED I1 I I 1 CLOSED m B TANKED OPENED 30am 0 TANKED 3D CLOSED NONE PATENTEDum 16 ms 3.765.449

MET 12 0F 16 B PRESSURIZED ZI CLOSED 2D A TANKED 2D OPENED ID 8 [PR C TANKED PMENTEDHCT 15 I973 SIEETIWFHB TABLE 0 coum- CYL- FUNC- VALVE non mom non PATENTED OCT 16 I973 FIG.9C2

AFFECTED VALVES 2D 8 ZPR NONE OPERATION OPENED CLOSED OPENED CLOSED VALVE CONDITION PRESSURIZED TANKED TANKED VALVE HYDRAULICALLY POWERED PUMP HAVING A PRECOMPRESSION FUNCTION This is a division, of application Ser. No. 886,687,

t filed Dec. 19, 1969 for Hydraulically, Powered Pump Having a Precompression Function now US. Pat. No. 3,650,638.

BACKGROUND OF THE INVENTION This invention relates to pumps of the multiplex type. More particularly, this invention relates to a multiplex pump of the type in which the pumped fluid is precompressed prior to discharge.

In the oil industry it has been common in the past to utilize multiplex pumps designed to deliver pumped fluid at high pressures on the order of 15,000 psi. or greater. It has been found that even the slight compressibility of this relatively incompressible pumped medium may result in a pulsating discharge pressure condition since a portion of the power intended to accomplish the discharge phase of each pumping cycle is inherently utilized to first compress the medium before it is brought to discharge pressure.

This discharge pattern is particularly undesirable where both high pumping pressure levels and very high delivery volumes are involved. The resulting pulsations could, under such conditions, subject the discharge conduits to severe vibrational forces. Thus, the pumping unit would be subject to stress conditions that might cause failure.

It would therefore, be extremely desirable to provide a pump that is capable of delivery of a high volume of fluid at high pressure levels without being subject to pulsation problems.

To this end the present invention involves the provision of a precompression function in the pump that continuously serves to bring pumped fluid to a pressure approaching discharge pressure prior to actual discharge. Thus, a relatively smooth constant pressure output of the pumped fluid may be obtained.

It has been previously proposed to provide a fluidoperated duplex pump (operable on a highly compressible fluid) with a precompression function in order to induce smoother discharge characteristics. This previously proposed pump is fluid operated in such a manner that one pumping unit is conditioned to undergo a discharge function while the other pumping unit undergoes both a suction and precompression function 'during the same time interval.

Although such a system may be satisfactory for some purposes, it may prove undesirable for a number of reasons. I I

For example, since all three functions associated with a pumping cycle (i.e., suction, precompression and discharge) are not simultaneously performed, there is an absence of constant pressure flow into the fluid end common to both pumping chambers. Therefore, the suctionline or suction header common to the two pumping units is subject to pulsating flow that may have undesirable consequences similar to those intended to be eliminated in connection with the discharge function.

Moreover, the lack of simultaneous performance of all three functions also prevents constant pressure flow of power fluid into and out of pressure and reservoir headers common to the power cylinders constituting the power end of the pumping unit. Thus, pulsation problems may also be created at the power end of the pump.

It would, therefore, be highly desirable to provide a multiplex pump which provides non-pulsating suction flow as well as discharge flow. It would also be desirable to operate such a pump with power fluid that flows into and out of the power end of the pump without pulsation.

Another disadvantage of the previously proposed pump stems from the direct utilization of pressurized power fluid to produce the stroking of the power plungers in each direction and in each cycle phase. Thus, the cycle in each pumping unit is not inherently functionally dependant upon the cycle in the other unit. As a result, a phasing error in one stroke, e.g., overtravel or undertravel of the power plunger during precompression, cannot be corrected without intervention by an operator so that the error may be self perpetuating.

Furthermore, the previously proposed pumping unit does not utilize the power fluid in the rod end of the power cylinder to a most efficient advantage. During discharge and precompression this fluid in the rod end may be exhausted to a power fluid reservoir where the potentialpower of this fluid, which is pressurized by the rod displacement, is lost. I

It would, therefore, be desirable to provide a multiplex pump with a precompression function and a selfregulating stroke control, as well as with efficient utilization of power fluid in the rod end of the power cylinder.

OBJECTS AND SUMMARY OF THE INVENTION It is therefore, a general object of the invention to provide a multiplex pump which obviates or minimizes disadvantages of the sort previously noted.

It is a particular object of the invention to provide an improved multiplex pump having a precompression function.

It is a further object of the invention to provide a multiplex pump which provides non-pulsating suction flow as well as discharge flow.

It is another object of the invention to provide such a multiplex pump which may be fluid operated with constant pressure flow of power fluid into and out of the power end of the pump.

It is a related object of the invention to provide a control valve assembly for such a multiplex pump which establishes cnstant pressure and flow of power fluid into and out of the power end of the pump.

It is still another object of the invention to provide a multiplex pump having a precompression function and means for automatically regulating the pumping strokes.

It is a related object of the invention to provide a multiplex pump having a precompression function and in which the stroking in each pumping unit is responsive to the stroking in the other units.

It is yet another object of the invention to provide an improved multiplex pump which may be fluid operated by the use of separate power and control circuits.

A preferred embodiment of the invention intended to accomplish at least some of the foregoing objects comprises a multiplex pump having at least three pumping units each operable in a cycle including suction, precompression, and discharge phases, with the cycles of each unit being out of phase with one another. The fluid end of the pump terminates in a common discharge line which is in fluid communication, with the discharge end of each pumping unit. Likewise, the suction ends of each of the pumping units are in communication with a common suction line. I

Operation of the pump according to the described cycle insures simultaneous performance of all functions associated with a given cycle to the end that constant pressure and flow of the pumped fluid occurs in the common suction line and in the common discharge.

line.

Each pumping unit is fluid operated by power fluid acting on a piston rod assembly extending between the fluid end and a power cylinder assembly at the power end of that unit. Each power cylinder assembly connected through a control valve assembly to a common flow line communication with a source of pressurized power fluid and a second common flow line communicating with a power fluid reservoir. By simultaneous performance of the suction, precompression and discharge phases of the cycle, a substantially constant pressure flow of the power fluid to and from these common flow lines is provided.

The control valve assemblies each include two sleeve valves communicating with a common chamber, which in turn communicates with a power cylinder. When one sleeve valve of a given control-valve assembly is in an open position and the other is closed, pressurized power fluid enters the associated power cylinder assembly to provide a discharge function in the fluid end ofthe associated fluid end cylinder assembly. When the sleeve valves are in a reversed position, a suction function is permitted resulting in discharge of the power fluid in the power cylinder assembly to the power fluid reservoir. During a phase of the cycle when both of these sleeve valves are in closed position, a precompression valve is opened, and power fluid is directed to the power cylinder through this precompression valve.

A separate control circuit is utilized to move the sleeve valves to their desired positions.

The rod ends of the power cylinders are fluid interconnected so that the functions in each pumping unit are performed in response to those performed in the other units. Also, a portion of the power circuit is interrelated with the control circuit to provide for selfcorrection of the stroke lengths in the power cylinder assemblies.

THE-DRAWINGS Other objects and advantages of the present invention will become apparent from the subsequent Since description thereofin connection with the accompany ing drawings in which:

FIG. I is a side elevational view partially broken away of a triplex pump according to the present invention;

FIG. 2 is a top plan view of the pump illustrated in FIG. I;

FIG. 3 is a front elevational view of the pump shown in FIG. 1, illustrating the control valve assemblies asso- 'ciated with the power end of the pump and the interconnection of the control fluid manifold blocks;

FIG. 4 is a partial cross-sectional view of one control valve assembly;

FIG. 5 is a cross-sectional view of a precompression valve employed in the control valve assembly of FIG. 4; 1

FIG. 6 is an exploded perspective view of the lower control fluid manifold associated with the control valve assembly of FIG. 4;

FIG. 7 is an exploded perspective view of the upper control fluid manifold associated with the control valve assembly of FIG. 4;

FIG. 7A is a cross-sectional view of the upper portion of the control fluid manifold in FIG. 7 and the check valves assembled therein;

FIG. 8 is a schematic illustration of-a power circuit and a control circuit of the present invention;

FIGS. 9A1, 981 and 9C1 are respectively schematic illustrations depicting the control valve conditions, the power circuit flow, and the power cylinder assembly functions respectively associated with the first, second and third phases of the pumping cycle;

TABLES A1, B1 and Cl. respectively provide an index of the valve conditions and cylinder functions depicted in FIGS. 9A1, 9B1 and 9C1;

FIGS. 9A2, 9B2 and 9C2 schematically illustrate the positions of the control circuit conditioning valves, the resulting movement of the control valves, and the control circuit fluid flow that accomplishes this control valve movement in the phases of the pumping cycle respectively associated with FIGS. 9A1, 981 and 9C1;

TABLES A2, B2 and C2 provide an index of the condition of the control circuit conditioning valves and an index of the control value movement associated with these conditionsas reflected in FIGS. 9A2, 982 and 9C2, respectively;

FIGS. 9A3, 9B3 and 9C3 schematically illustrate the tripping of the cycling valves and the resulting control circuit fluid flow that causes the positioning of the control circuit conditioning valves illustrated respectively in FIGS. 9A2, 9B2 and 9C2; and,

TABLES A3, B3 and C3 provide an index of the tripped valve and its affect on the control circuit conditioning valves as respectively illustrated in connection with FIGS. 9A3, 983 and 9C3.

DETAILED DESCRIPTION General Summary:

Referring now to FIGS. 1 and 2, an overall view of a triplex pump 20 according to the present invention is there shown.

The pump 20 includes a fluid end assembly 22 comprising three substantially identical cylinders 24. The fluid end assembly is of the type utilized in the HT--400 pump series referred to on page 6 of the 1968 Sales and Service Catalogue of I-Ialliburton Services,'Duncan, Oklahoma.

The internal passages 26 of each of the fluid end cylinders 24 are each in communication with a valved pump cylinder head 28 of the type more particularly described in US Pat. No. 3,259,075, assigned to the assignee of the present invention. The disclosure of this patent is hereby incorporated by reference. Each of the cylinder heads 28 is provided with a conventional suction valve assembly 30 and a conventional discharge valve assembly 32. The discharge valve assemblies 32 communicate with a common discharge manifold 34, and the suction valve assembly similarly communicates with a common and conventional suction loader (not shown). I

Extending from the fluid end assembly 22 in a direction away from the chambers 28 is a power end assembly 38. The power end assembly 38 includes three substantially identical power cylinders 40 having internal passages 41. Each of these power cylinders 40 is in generally longitudinal alignment with one of'the fluid end cylinders 24. A piston rod assembly 42 extends longitudinally into each power end cylinder 40 and the aligned fluid end cylinder 24. The ends of the piston rod' assemblies 42 which extend into the chambers 26 of the fluid end cylinders 24 are provided by capped plunger ends, which function as pumping pistons 44 that are operable to bring about suction and discharge action in a conventional manner, and precompression action in a manner hereinafter more fully described.

The opposite ends, or power pistons, 46 of the piston rod assemblies 42 are in sliding and sealed engagement with the walls of the internal passages 41 of the power cylinders 40. In a manner hereinafter more fully described. power fluid acts on opposite faces 48 M950 of the power pistons 46 to reciprocate the piston rod assemblies 42.

The power end assembly 38 and the fluid end assembly 22 are separated by a spacer frame assembly 51 which permits the fluid end piston rods, or plungers, 52 and the power end piston rods 54 to be separate members thereby facilitating maintenance operations. These rods 52 and 54 are each hollow, cylindrical members sealingly received in the fluid end cylinder passages 26 and the power end cylinder passages 41, as indicated at 55 and 56. If desired, a floating annular rod seal may be employed so as to allow the rods to operate slightly eccentric to the power cylinder bores, thereby eliminating the necessity of extremely accurate align ment between the power cylinders and the fluid end cylinders.

Extending longitudinally of and internally of each of these members are tie rods 57 which are joined at one end to the pistons 44 and 46 and at the opposite end with a cam actuator 58 to form, together with the rods 52 and 54 and their associated piston means 44 and 46, the integral piston rod assembly 42. The permissible stroke length of each piston rod assembly 42 is such that each cam actuator 58 is movable between a back position adjacent the power end cylinders 40 and a forward position adjacent the fluid end cylinders 24.

In a manner hereinafter more fully described, the cam actuators 58 are operable, in connection with cycling valves FP, to provide a signal that the piston rod assembly has reached its forward position. These cycling valves F? are mounted on the spacer frame 51 at that forward position by suitable mounting means, indicated at 59. The location of this mounting means is such that the lengths of the cam actuator 58' cooperate with the valves FP for a time sufficient to permit the necessary circuit functions to take place.

In a similar manner, at least one cam actuator 58 is operable, in connection with a stroke control valve HP, to provide a signal that its associated piston rod assembly 42 has reached its back position. This stroke control valve 8? is also mounted on the spacer frame 51 at that back position by suitable mounting means 60.

At the end of the power cylinders 40 remote from the fluid end assembly 22, each power cylinder is in continuous communication with one of three identical control valve assemblies CV. To facilitate description of a pump of the present invention, the three control valves are hereinafter referred to as ll-CV, 2-CV and 3-CV, respectively. Similarly, the hereinafter described identical portions of the CV valve assemblies are differentiated by the prefixes 1-, 2- and 3-, as are the associated power cylinder assemblies 40.

The function of the control valves CV is to direct power fluid to and from the power cylinders 40 in a manner such that the power cylinders each operate on a suction, precompression, discharge cycle, each out of phase with one another.

In the discharge phase of the cycle in a given power cylinder 40, power fluid acts on the outer face 50 of a power piston 46 to transmit force through the piston rod 42 so as to cause the fluid end piston 44 to move to its forwardmost stroke position whereby fluid in the cylinder head 23 is expelled to the common discharge manifold 34. Prior to the discharge phase of the cycle, this fluid has been precompressed by power fluid acting on the power piston face 50 after passing through a precompression valve PR mounted on the control valve assembly CV. This precompression flow of power fluid causes the power piston 46, through the piston rod assembly 42, to move forward by in increment sufficient to compress the fluid to be pumped and thereby raise the pressure of the fluid to approach the discharge pressure.

Suction movement of each power piston 46 is caused by power fluid acting on the inner face 48 of the power piston 46. The internal passages 41 of the power cylinders 40 are fluid interconnected in a normally closed circuit by a suitable common conduit 61. Thus fluid in two rod ends of the passages 41, which fluid is displaced during precompression and discharge movement of the associated power pistons 46, is caused to flow through this common conduit 61 into the third passage 41 to act on the inner face 48 of the power piston 46 in that third passage 41.

in this manner, the suction, precompression and discharge functions are simultaneously and responsively performed, one function being performed in each fluid end cylinder 24. Therefore, constant pressure flow continually exists between the fluid end of the pump and the common suction header and common discharge manifold 34.

For purposes of accomplishing automatic stroke correction, as hereinafter more fully described, the common conduit 61 connecting the rod ends of the power cylinders 40 is in fluid circuit with a conventional accumulator 62 and with a source of power fluid through a normally closed filling valve (not shown in FIG. 1 hereinafter described. Also, a rod end relief valve 222 provides selective communication between the rod ends and a power fluid reservoir.

Also, as hereinafter described, the control valve assemblies CV which direct the power fluid, preferably water, are, in theillustrated embodiment, monitored by a separate control fluid circuit, preferably utilizing a different fluid such as oil, air or a combination thereof. it will, however, be apparent that controls other than a control fluid circuit (e.g., an electrical sensing arrangement) may be utilized to monitor the power circuit.

It will be appreciated that the elements of the control circuit, the control valve assemblies CV, the power end assembly 38, and the fluid end assembly 22, may all be mounted on a suitable common frame such as a skid 64. Preferably the mounting on the skid is designed to permit the fluid end cylinders 24 and the power end cylinders 46) to move longitudinally for a limited distance, during reciprocation of the piston rod assemblies 

1. A control valve assembly for directing fluid to and from the power end of a piston and cylinder assembly, the control valve assembly comprising: power fluid inlet valve means having power fluid entry and exit passages, power fluid discharge valve means having power fluid entry and exit passages, said entry passage of said inlet valve means being in continuous communication with a source of pressurized power fluid, a common chamber in essentially closed fluid circuit with said power end of said piston and cylinder assembly and in continuous communication with said entry passage of said discharge valve means and selective communication with said exit passage of said inlet valve means while said entry passage of said inlet valve means remains in continuous communication with a source of pressurized power fluid; and said exit passage of said discharge valve means being in selective communication with a power fluid reservoir while said entry passage of said discharge valve means remains in continuous communication with said common chamber, said control valve assembly further including: precompression valve means having power fluid entry and exit passages, said precompression valve means exit passage being in continuous communication with said common chamber through power fluid flow reducing means, and said precompression valve means entry passage being in continuous communication with said source of pressurized power fluid, and being in selective communication with said common chamber through said precompression valve exit passage.
 2. A control valve assembly according to claim 1 including: valve operating means for selectively conditioning said inlet valve means, said discharge valve means, and said precompression valve means to provide one of established fluid communication between said common chamber and a. said power fluid reservoir through said discharge valve means, b. said source of pressurized power fluid through said inlet valve means, and c. said source of pressurized power fluid through said precompression valve means.
 3. A control valve assembly according to claim 2 in combination with at least two other control valve assemblies according to claim 2, wherein: said valve operating means of each of said control valve assemblies are interrelated with each other and are cyclically operable to provide, during any cycle phase, a different one of said established fluid communication between its common chamber, and a. said power fluid reservoir through its discharge valve means, b. said source of pressurized fluid through its inlet valve means, and c. said source of pressurized fluid through said precompression valve means.
 4. A control valve assembly according to claim 3, wherein each of said valve operating means comprises: control fluid valve means for positively maintaining said inlet valve means and said discharge valve means against drifting to a different condition during any cycle phase.
 5. A control valve assembly comprising: power fluid inlet valve means having power fluid entry and exit passages, power fluid discharge valve means having power fluid entry and exit passages, said entry passage of said inlet valve means being in continuous communication with a source of pressurized power fluid, said exit passages of said discharge valve means being in selective communication with a power fluid reservoir, and a common chamber in continuous communication with said entry passage of said discharge valve means and selective communication with said exit passage of said inlet valve means, said control valve assembly including: precompression valve means having power fluid entry and exit passages, said precompression valve means exit passage being in continuous communication with said common chamber through power fluid flow reducing means, and said precompression valve means entry passage being in continuous communicatioN with said source of pressurized power fluid, and being in selective communication with said common chamber through said precompression valve exit passage.
 6. A control valve assembly according to claim 5 wherein each of said sleeve valves includes an external periphery defining a piston means having opposite piston faces forming the ends of opening and closing actuating chambers, said assembly further including: control valve means for selectively directing control fluid to and from said opening and closing actuating chambers to move said sleeve valves to and from positions providing the selective communication between said common chamber and said exit and entry passages.
 7. A control valve assembly according to claim 5 wherein the ends of said inlet and discharge sleeve valve means define said entry and exit passages thereof and wherein: said ends of said sleeve valve means defining said exit passages are each receivable in a generally cylindrical spacer means having closed ends defining a sleeve valve seat, and lateral slots, said sleeve valve means each being movable to a closed position blocking fluid communication between said common chamber and said slots when said ends defining said exit passages are seated against said valve seats, said sleeve valve means each being movable to an open position permitting communication between said common chamber and said slots.
 8. A control valve assembly according to claim 7 including: valve operating means for moving said discharge sleeve valve means to its open position in two discrete stages.
 9. A control valve assembly according to claim 8 wherein: each of said sleeve valve means has an outer diameter smaller than the inner diameter of the one of said spacer means in which it is received.
 10. A control valve assembly according to claim 5 wherein: said inlet valve means and said discharge valve means are sleeve valves generally longitudinally aligned with said common chamber therebetween. 